BZX85 is just the series and the 0 might be a C actually (BZX85/C ZENER Diodes)?
anyways, i would go through the circuit step by step, starting with measuring the voltage at the switching tip of the input sockets to see what's the offset voltage (ZENER controlled).

BTW did you already check the continuity of all connections of the non-working channels? without pondering too much i just smells like a wrong wired potentiometer (however it is funny that two channels behave the same way - but things happen and the both channels are not connected to each other, so...)._________________
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)

The CCW ends of the potentiometer are all connected to the ground.
The voltages of the wipers 4 depends on potentiometer of 1? That is strange....
pots 2, 3 and 5 go from 0V to 6.4V._________________Weblog!

tomorrow i will have the time to ponder upon your measurements.
however, from a 1st look at your measurements and observations i would say: replace and rewire potentiometer 1.
it should work as a voltage divider, so the voltage at CW should always be the reference voltage from the ZENER, whilst the voltage on the wiper should change from 0V to reference voltage (CW).
maybe there is a short between CW and wiper (inside the pot, or at the board). then the potentiometer would act as a variable resistor, not as a voltage divider. this would cause a change in the reference voltage, as far as i can see now (without looking at the schematic and thinking more about it), thus affecting the other channels..._________________
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)

Thanks for the help. Replaced the pot, and now channel 1, 2, 3, and 5 are working great. Channel 4 remains on 5.81V whatever setting of the pot, and the mix out remains at -9.3V
Time to track down those problems _________________Weblog!

Oh sorry Matthias, I can't work on modules on monday to fridays, as the modular is at my parents (have more room there)
I'll measure the other pins on friday evening Thanks for the help!_________________Weblog!

All pots on the 0 (center) position. Potentiometer 4 in the CCW position, voltage across wiper and right pin: 0V. Center position: 3.2V, CW position: 6.4V
Whatever the position of pot 4, the output voltage of channel 4 is 5.89V._________________Weblog!

All pots on the 0 (center) position. Potentiometer 4 in the CCW position, voltage across wiper and right pin: 0V. Center position: 3.2V, CW position: 6.4V

this is what you measured for the other pots, and this is as it should be: it's working as a volage divider.

Quote:

Whatever the position of pot 4, the output voltage of channel 4 is 5.89V.

so we should take a closer look at the other path the voltage goes. check all connections (continuity) of the trimmer T4 and it's accossiated parts. compare the voltages you measure here (behind the trimmer) with those of the other working channels (same potentiometer settings). the opamp is trying to balance the difference between the both inputs, so since the potentiometer side is okay, the error will be at the trimmer/feedback side..._________________
cheers,
matthias
____________
fonitronik at
FlickR (pix) / SoundCloud (sounds) / YouTube (vids) / Vimeo (vids) / facebook (news)

Ok, got channel 4 fixed, the opamp didn't work, and there was no voltage across the trimmer. Still the mixer doesn't work. Tim to fix that
Edit: near the C9 capacitor is a white line on the silk screen. Should that be a wire connection? _________________Weblog!

Just wiring up now, and I notice there are no diagrams and not even a description on how to wire the 3 pole switch in the documentation.

Looking at the board so the text on the switch section of the board is facing myself: There are 3 U shaped indicators on the board relating to the switch. the way I have it wired is the first, third and fifth (the left of each U) connect to the bottom row of the switch, and the 2nd, 4th and 6th (the right of each U) connect to the centre row on the switch.

I don't know if that is correct or if it is related, but the fault I have is when all the pots are centred (and nothing connected) the +LED is glowing softly. If I turn any of the pots clockwise it goes off, if I turn them anticlockwise it glows brighter, and the more pots anticlockwise also brings the -LED on at the same time.

Plugging something into the output disables the pot associated with that output, and moving the trimmer does nothing.

Does anyone have a wiring diagram for the switch, or does it look like I have wired it properly and my fault maybe lies elsewhere?_________________

Looking at the board so the text on the switch section of the board is facing myself: There are 3 U shaped indicators on the board relating to the switch. the way I have it wired is the first, third and fifth (the left of each U) connect to the bottom row of the switch, and the 2nd, 4th and 6th (the right of each U) connect to the centre row on the switch.

correct. if the switch is open, the module is in AC mode. the LEDs shall not be lid then. if the switch is closed, the passive filter on the summed output is bypassed, and the module is on DC mode. the LEDs should work in this mode.

Quote:

I don't know if that is correct or if it is related, but the fault I have is when all the pots are centred (and nothing connected) the +LED is glowing softly. If I turn any of the pots clockwise it goes off, if I turn them anticlockwise it glows brighter, and the more pots anticlockwise also brings the -LED on at the same time.

there is something wrong. the +LED should get brighter when any pot is turned clockwise, and darker when any pot is turned counter clockwise.

Quote:

Plugging something into the output disables the pot associated with that output, and moving the trimmer does nothing.

plugging any single out should just remove this output from the sum (thus you won't see any effect on the LEDs then). however, the pot should still work for this channel/single out.

Quote:

...fault maybe lies elsewhere?

i believe so.

IMHO most errors are wiring related. some suggestions:
just triple check the pots wiring.
check the orientation of the +LED.
each input is normalled to 5V. check and follow this voltage of a channel throughout the entire circuit using a multimeter (does it appear on the switching contact of the input socket? does it appear on the single output socket? does it appear at the summing stage? does it appear at the LED driver?).
try to follow the calibration instructions.

You cannot post new topics in this forumYou cannot reply to topics in this forumYou cannot edit your posts in this forumYou cannot delete your posts in this forumYou cannot vote in polls in this forumYou cannot attach files in this forumYou can download files in this forum

Please support our site. If you click through and buy from our affiliate partners, we earn a small commission.